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I had to make a 3/8" UNF 2 3/4" long cap head bolt by cutting down a long 3/8" BSF cap head bolt and screwcutting the thread on it (this was to repair a Hytork hydraulic tightening head) We didn't have the correct length cap heads in stores. It would have delayed the job (boiler feed pump rebuild) if we had to wait for the correct bolts.
Be aware, 10.9 cap bolt material is tough stuff, Luckily i had the gear (large MT4 tailstock die holder) and was able to screwcut under power. Used Rocol cutting paste as its the best i have found.
I know the purists will say the thread should be rolled, but it works.
I doubt you will find any suppliers of off the shelf CEI threaded cap bolts. The market for them will be tiny.
The long extended through cap bolts that Merlin used on the DOHC head were screwcut from longer ones, and that was 45 years ago... Interestingly the short head bolts were 3/8" UNF cap bolts tapped into the barrel casting. I think they had access to raw barrel castings and machined them to there own spec, ditching the CEI thread and using UNF instead

<blockquote data-quote="dobba99" data-source="post: 659211" data-attributes="member: 5834">I had to make a 3/8&quot; UNF 2 3/4&quot; long cap head bolt by cutting down a long 3/8&quot; BSF cap head bolt and screwcutting the thread on it (this was to repair a Hytork hydraulic tightening head) We didn&#039;t have the correct length cap heads in stores. It would have delayed the job (boiler feed pump rebuild) if we had to wait for the correct bolts.Be aware, 10.9 cap bolt material is tough stuff, Luckily i had the gear (large MT4 tailstock die holder) and was able to screwcut under power. Used Rocol cutting paste as its the best i have found.I know the purists will say the thread should be rolled, but it works.I doubt you will find any suppliers of off the shelf CEI threaded cap bolts. The market for them will be tiny. The long extended through cap bolts that Merlin used on the DOHC head were screwcut from longer ones, and that was 45 years ago... Interestingly the short head bolts were 3/8&quot; UNF cap bolts tapped into the barrel casting. I think they had access to raw barrel castings and machined them to there own spec, ditching the CEI thread and using UNF instead</blockquote>

[QUOTE="dobba99, post: 659211, member: 5834"] I had to make a 3/8" UNF 2 3/4" long cap head bolt by cutting down a long 3/8" BSF cap head bolt and screwcutting the thread on it (this was to repair a Hytork hydraulic tightening head) We didn't have the correct length cap heads in stores. It would have delayed the job (boiler feed pump rebuild) if we had to wait for the correct bolts. Be aware, 10.9 cap bolt material is tough stuff, Luckily i had the gear (large MT4 tailstock die holder) and was able to screwcut under power. Used Rocol cutting paste as its the best i have found. I know the purists will say the thread should be rolled, but it works. I doubt you will find any suppliers of off the shelf CEI threaded cap bolts. The market for them will be tiny. The long extended through cap bolts that Merlin used on the DOHC head were screwcut from longer ones, and that was 45 years ago... Interestingly the short head bolts were 3/8" UNF cap bolts tapped into the barrel casting. I think they had access to raw barrel castings and machined them to there own spec, ditching the CEI thread and using UNF instead [/QUOTE]

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